Tycho was the official astronomer to the King of Denmark. At the Royal Observatory at Uraniburg he used the best instruments available before the invention of the telescope to measure the positions and motions of the planets and stars. His assistant was young German Johannes Kepler, who would in time achieve his own fame.
Tycho the Man
Tycho Brahe, born Tyge Ottesen Brahe (December 14, 1546 - October 24, 1601), was commonly known as "Tycho" rather than "Brahe," and was a Danish nobleman known for his comprehensive and accurate astronomical observations. Tycho devoted himself to improving observation techniques. He was granted an estate on the island of Ven where he built an observatory where he did his observations and precise measurements of his astronomical findings.
Tycho the Astronomer
As an astronomer, Tycho worked to combine the geometrical benefits of the Copernican system with the philosophical benefits of the Ptolemaic system into his own model of the universe, known as the Tychonic system. He was assisted by Johannes Kepler, who later used Tycho's astronomical information to develop his own theories and derive the laws of planetary motion. Before Tycho, no one had attempted to make many observations. He catalogued the planets and stars with enough accuracy so as to determine whether the system of Ptolemy or Copernicus was more valid in describing the heavens.
Discovery of a New Star Nova
In 1572, Tycho saw a 'new star' Nova which was not there before in the constellation of Cassiopeia. Prevailing knowledge held that the heavens were unchanging, so the 'nova' had to lie within the Earth's atmosphere, where nature was subject to change and decay. His measurements showed that the new star did not change its position relative to the stars around it during the year it was visible. So it had to be out among the stars, not close at hand. It was a momentous discovery.
More Observations
Following the revelation of his 'new star' Tycho continued to challenge the accepted model of the universe of Copernicus. In 1577 he followed the path of the comet with his precise instruments, showing that they were distant objects, lying far beyond the Moon, and not just phenomena in our own atmosphere. Its track seemed to cut across the orbits of the planets, which could therefore not be hung from crystalline spheres as still believed. Nor were the orbits of the comets perfect circles, but greatly elongated. Slowly, the old universe of Aristotle and Ptolemy was being unraveled.
Tycho's Theory of the Changing Heavens
Tycho did not go all the way with Copernicus. If the Earth really did orbit the Sun, all the stars should have shown some degree of 'parallax,' moving back and forth by different amounts as the viewpoint from Earth changed. He could see no such movement. This meant that either the Earth did not move at all or the stars were too far away from the parallax to be observed. He settled for the first option. In his model of the universe, the five known planets orbited the Sun, but the Sun and the Moon orbited the Earth which is still the centre of the universe.
Others went beyond Copernicus. More experiments and observations went on. Tycho left behind his successors huge accumulations of measurements about the movements of planets and stars. His one-time assistant, Johannes Kepler, used them to the fullest to later unravel the laws of planetary motion.
Sources:
Biographical Dictionary, edited by Una McGovern, Chambers, 2002
Ellyard, David. Who Discovered What When. New Holland, 2005
Verma, Surendra. The Little Book of Scientific Principles , Theories & Things. New Holland, 2005
